Radiation and Cancer Biology

MO 19 - Biology 7 - Normal Tissues

1235 - Mid-Treatment [18]F-FDG PET Uptakes Can Predict Symptomatic Radiation Pneumonitis in Non-Small Cell Lung Cancer Patients

Wednesday, September 18
8:40 AM - 8:45 AM
Location: Room W192

Mid-Treatment [18]F-FDG PET Uptakes Can Predict Symptomatic Radiation Pneumonitis in Non-Small Cell Lung Cancer Patients
A. Ajdari1, N. Shusharina1, Z. Liao2, R. Mohan3, and T. Bortfeld1; 1Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 2Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 3Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX

Purpose/Objective(s): Non-small cell lung cancer (NSCLC) is one of the areas where the outcome of radiation therapy (RT) has still room to improve. Personalization of the treatment plan, especially if done mid-treatment, can play an important role in improving treatment outcome. For the full potential of this personalization to be realized, there is a need for accurate and predictive biomarkers of response to treatment. We investigated the predictive ability of mid-treatment [18]F-fluorodeoxyglucose (FDG) PET data in assessing lung tissue sensitivity and symptomatic radiation pneumonitis (RP) in NSCLC patients.

Materials/Methods: Inoperable stage II-III NSCLC patients for whom pre- and mid-treatment FDG PET-CT data was available were included in our study. Incidence rate was defined as ≥ grade 2 symptomatic RP (denoted as RP+) at 12 months after RT completion. Images were registered using rigid and B-spline deformable registration to get a voxel-to-voxel disposition mapping. Dose accumulation and PET standard uptake value (SUV) calculation were subsequently performed in the normal lung (total lung excluding GTV). Difference between pre- and mid-treatment SUV values (Δ-SUV) were used to characterize the mid-treatment lung tissue response (i.e., higher inflammation, uptake in metabolic activity). Difference between RP+ and RP- groups in terms of Δ-SUV metrics was statistically analyzed. Linear regression was used to describe voxel-wise dose and SUV relationship for each patient. Multivariate logistic regression was performed to assess the association between RP and several dosimetric and biological factors, including SUV uptakes, GTV volume, and mean lung dose (MLD).

Results: 27 patients who underwent treatment with proton and IMRT were analyzed. 6 patients (22%) were classified as RP+. In virtually all the mid-treatment Δ-SUV metrics (i.e., SUV5, SUV10, SUV40, peak SUV, and mean SUV), there was a significant difference between RP+ and RP- groups (p-value 0.05 in all cases). Additionally, we found a significant difference in mid-treatment SUV-dose slope between the two groups (p-value = 0.04). Specifically, RP+ patients showed steeper slopes (0.034, range 0.010-0.090), compared to RP- patients (0.002, range -0.002-0.021). This difference was more pronounced (p-value = 0.03) in the higher-dose region (i.e., receiving dose ≥ 30Gy). The results of the logistic regression revealed that MLD and mid-treatment SUV-dose slope were significant contributors to RP. This was consistent with previous findings showing the predictive ability of MLD and post-treatment slope.

Conclusion: The uptake of the mid-treatment FDG PET can be used as the biomarker for assessing lung tissue sensitivity and early detection of acute symptomatic radiation pneumonitis. Mid-treatment FDG data has the potential to be used in biologically-adaptive treatment planning and personalized treatment.

Author Disclosure: A. Ajdari: None. N. Shusharina: None. Z. Liao: Past Chair; ASTRO IES. R. Mohan: Research Grant; National Cancer Institute. Stock; General Electric. Member, International Advisory Committee; CERN. Member; Scientific Advisory Board. T. Bortfeld: Research Grant; RaySearch AB, Stockholm Sweden.

Ali Ajdari, PhD

Massachusetts General Hospital

Disclosure:
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Massachusetts General Hospital, Harvard Medical School

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